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Friday, July 21, 2017

K.P.S. Kang's Minimalist VXOs (and one for the BITX)


K.P.S. Kang provides us with some great ideas for simple VXOs.  He includes an intriguing reference for a 5 MHz circuit useable in a BITX.  Tell us more OM! 


Tuesday, July 18, 2017

NYC's Radio Row Survives (sort of) in the Bronx

Thanks to our friend (and official lexicographer) Steve Silverman KB3SII for alerting us to this important bit of radio news from the Big Apple.  It seems that a part of old Radio Row was saved and moved -- first to Brooklyn and now to the Bronx.   I got a kick out of some of the comments in the New York Times article about the store:  The insurance company determined that the contents of the store were "non-pilferable." And one young audio enthusiast was quoted as saying that old American tubes "sound better" than Chinese tubes.  I guess they have more presence.  Or brightness.  And less feathering.  Or something.

Here is the 2011 NYT article: 
http://www.nytimes.com/2011/11/20/nyregion/leeds-radio-is-a-haven-for-lovers-of-all-things-analog.html   


To N2CQR  

Sunday, July 16, 2017

Excellent Description of the Electret Microphone

I've been experimenting with electret replacements for the D-104 crystal element.   I found this site with a really excellent description of what lies inside those little electret capsules.  Here it is: 

http://www.openmusiclabs.com/learning/sensors/electret-microphones/index.html

Saturday, July 15, 2017

Dino's FB W1FB Crystal Tester

A couple of weeks ago I noted that the complexity of DeMaw's circuit caused many of us to wimp out on this test gear project.  I joked that those who had built the device might be able to set up small businesses to do the testing for the rest of us.  Perhaps our friend Dino can cut a deal with G7WKE to divide up the world market for crystal testing: Dino could have the Western Hemisphere while Rob covers Europe and points East.  

Bill -

Enjoyed seeing someone else who has built Doug’s crystal tester on the blog.  Here’s mine, built this back in early 2007.  Anyone who wants to duplicate the tester can find the article in the January 1990 issue of QST or the updated article in the W1FB Design Notebook (page 192).  Note that the QST article has a missing component value and a missing component (both corrected in the Design Notebook):

(1) R24 is missing its value - it’s marked in the Notebook as 56 ohms.

(2) There should be a 220 ohm resistor connected between the output pin of U2 the LM317T regulator and the top of R1 the voltage adjust pot that is connected between U2’s adjust pin and ground [corrected in the March 1990 QST Feedback column].

I built a FT-243 adapter to let me work with larger crystals.

73 - Dino KL0S





Friday, July 14, 2017

And Now For Something Completely Different: 70cm FM

So there I was, talking to KE5FV on my scratch-built 17 meter BITX, when in walks my son Billy with this walkie talkie.  "Hey Dad, I'm cleaning out my room -- could you use this?"  I'd seen it before but I thought it was some Family Radio Service device that he had picked up.  But no!  It is one of those very cheap Baofeng UV-5R FM transceivers.  I soon found myself scrolling through menus, trying to figure out how to use the strange new appliance. 

I got it on 70cm and soon established contact with a Bill W3HXF -- that was my first ever UHF contact.  We then switched to 2 meter simplex. 

It works fine.   I've been looking for something different.  This could be fun.  Any suggestions on how to make the most use of this thing?

Sunday, July 9, 2017

Have You Ever Seen What's Inside a D-104 Crystal Element?

I had not seen this  I must say, I am disappointed.  I had visions a circular collection of shiny Rochelle salt crystals.  But look at this thing.  It is quite flimsy -- not at all what you'd expect from the sturdy D-104 exterior.  It has kind of a "Wizard of Oz" behind-the-curtain feel to it.  Yuck. If I can't find a D-104 element in good shape, I might reach for a dynamic element or -- gasp -- an electret.

Saturday, July 8, 2017

Stop Me Before I Commit an Electronic Atrocity!

Sadly, not mine
I like the D-104 mic.  I bought one from Astatic shortly before they went under and it has provided good service with many different rigs for a long time.

I wanted another one, primarily for my DX-100/HQ-100 station.  I saw one on e-bay and a few days later it was here.  Unfortunately the seller was correct when they warned that it showed no output.  I had hoped it was a problem with the amp in the base, but no, it seems that the crystal element is quite dead.  It is an MC320 cartridge marked 7-77.  There is an aluminum sheet at the front that is apparently supposed to be riding atop a center support that connects mechanically with the magic crystals.  But it looks like a circular tent that has poked through the center support and collapsed around it.

Just a few years ago there were some options for replacement elements, but it seems that most of these are gone.  Bob Heil does have a dynamic element replacement kit for about 68 bucks. 

There are many schemes for putting electret elements in the old D-104 head...  I was reaching for the junk box but I stopped myself.  NO!  I will try not to commit this kind of electronic barbarity. (I have already sinned by killing several QF-1 Q multipliers and a couple of Benton Harbor lunch boxes.)  I will instead turn to the SolderSmoke brother/sisterhood and ask if anyone out there has a crystal element that could bring this old mic back to life.  My DX-100 deserves nothing less. 

Anyone have a D-104 crystal element in their junk box? 
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column